Help: Replacing plasterboard

Hello Everyone,

I'm looking for some help, I've done a search and the results are relating only to specific problems or are only partially related.

We've just started to rmove some tiles from our bathroom walls with results ranging from really good, to 'Oh my God! There's a whopping great big hole in the plasterboard!". Therefore, rather than continue the agony of tile removal. We've decided to literally cut our losses and cut the tiled section of plasterboard out of the wall and replace it with a new one. All good in theory, but I'm a novice who hasn't even laid a tile in his life and I haven't a clue how to do this, so I'm really looking for a bit of advice and direction as to the best way to go about this.

Our bathroom walls are plasterboard ontop of some wooden strips/slats/batons, and what I was intending to do was cut the tiled section of the wall away, replace with a new section and then secure to the strips/batons. As this should give us a perfectly flat surface for the new tiles to go on.

Is this the right approach? And if so, what's the best way/tool to use to cut out plasterboard (saw? Stanley knife?)? Then to get the new piece of plasterboard to the correct size what's the best tool to use (again, saw? Stanley knife?)? And finally, once at the correct size whats the best method of securing to the batons/strips (screws? nails?)?

I would be really grateful for any advice you can give.

Many thanks,

Mark